Page
64
LTO SCSI Interface Manual
MODE SENSE
The MODE SENSE command allows the host to determine various drive parameters.
These parameters are sent from the drive to the host as data formatted in a
parameter list. This command is complementary to the Mode Select command that
sets device parameters.
The drive terminates execution of the Mode Sense command:
•
When the number of bytes specified in the Allocation Length field have been sent
to the host, or
•
When all available Mode Sense data has been sent to the host.
If a Mode Select command has not been performed since power-on or SCSI Reset,
the default mode parameters are in effect.
All Mode Select parameters may be rounded up or down, as appropriate. A Mode
Sense command may be issued after a Mode Select command to determine which
parameters have been rounded.
Block and page descriptions for this command are shown below and on subsequent
pages.
Command Descriptor Block
6-Byte Command Descriptor Block
Byte
Bits
7
6
5
4
3
2
1
0
0
Operation Code (1Ah)
1
Ignored LUN Reserved DBD
Reserved
2
PC
Page Code
3
Reserved
4
Allocation Length
5
Control
Field Descriptions
Field
Bytes
Bits
Description
Operation
Code
0
The Operation Code for the 6-byte version of Mode Sense is 1Ah.
Ignored
Logical
Unit
1
5-7
The LUN field is residual from the SCSI-1 days and is ignored.
DBD
1
3
0 = Return the block descriptor in the Mode Sense data.
1 = Disable Block Descriptors (DBD).
NOTE: When the DBD is 1, the Block Descriptor Length in the pa-
rameter header is 0.
